The present invention relates to a measuring system for measuring the relative position of first and second objects, of the type comprising a scale which is secured to the first object, and a scanning unit which is secured to the second object to scan the scale.
When such measuring instruments are used in harsh environments such as those associated with many processing machines, the measuring system for measuring or adjusting the relative position between a tool and a workpiece must often be fastened to a machine part which, during the operation of the processing machine, heats severely with respect to the workpiece that is to be measured or processed. In this event, the scale of the measuring system is typically heated as well, and the scale expands, so that measuring errors can result. One prior art approach to overcoming such measuring error is to provide a scale of a material having a negligibly low coefficient of thermal expansion for such measuring systems. Such a scale can be formed of quartz glass or Invar. However, such a scale is relatively expensive to manufacture.